We have been continuously told by Bob Ainsworth, the defence secretary, that the Treasury reserve is paying for the full cost of operations in Afghanistan. On Monday, Gordon Brown told us the same thing in the House of Commons. And then the following day the truth behind that spurious claim was revealed. Indeed, Ainsworth proudly acknowledged the fact.

After the government's announcement this week on massive defence cuts nobody can dispute that the Ministry of Defence's core budget is being raided to pay for current operations. Yet, this should come as no surprise. It is well known that Gordon Brown, as chancellor, was never willing to fund Tony Blair's wars. He cut the helicopter budget by £1.4bn in 2004, when we were at war in both Iraq and Afghanistan. So while the announcement of additional Chinooks was welcome, were it not for Labour's disastrous decision in 2004 we could have had them in theatre today, helping to save lives.

What we saw yesterday was a result of Labour's catastrophic mismanagement of the economy over the last decade. Our defences are being cut, not because the threats to the UK are diminishing, but because a decade of incompetence has left the MoD budget in tatters. We are losing core capabilities which are crucial to our ability to respond to the unexpected.

I asked Ainsworth a number of questions on Tuesday and received an answer to just one. The government is planning to withdraw from service next spring the Nimrod MR2, crucial to anti-submarine warfare, long-range rescue and reconnaissance missions. But introduction into service of its replacement, the Nimrod MRA4, has been delayed for two and a half years – during this time Nimrod crews will be forced to train on flight simulators to maintain their capability. He didn't say how our submarines will be protected in that two-year gap.

He said that army training would be reduced, but he didn't say which aspects of it were going to be cut and what impact that will have on the army's readiness to deploy at short notice. Further delays to the aircraft carriers and the downgrading of facilities in Cyprus were heavily trailed in the media, but he didn't say if those had been considered or would go ahead.

Bernard Gray's report in October, and this week's National Audit Office report both concluded that there was a potentially disastrous black hole looming in the MoD's budget. The Institute of Fiscal Studies warned that the pre-budget report could mean large cuts in the defence budget over the next three years. He didn't say how big any of those cuts might need to be.

He did not say whether the Chinooks would be funded from the cancellation of the future medium helicopter (FMH) programme. He didn't explain how the RAF fast jets' ability to respond to the unexpected would be affected by the closure of RAF Cottesmore. Nor did he detail what might happen to the defence training review and St Athan.

These are all important questions that need to be answered.

The government is mortgaging our current and future security to pay for the shortfall in current operations. We need a proper foreign-policy led strategic defence review, not a piecemeal mini review by stealth, which is what this week's announcement was.

We will not be in Afghanistan forever. If General Sir David Richards is right, then by the time these extra Chinooks arrive in Helmand, we should hope to have handed over a large part of the mission to Afghan forces. Meanwhile, Iran has the potential to mine the Gulf, and the government is removing one of the Royal Navy's minehunting vessels – one of the main maritime capabilities America appreciates the most from the Royal Navy.

The world is not getting any safer – in fact, it is getting more dangerous. My worry is that the government's approach will leave Britain vulnerable. When the first duty of government is the defence of the realm, that could be New Labour's most terrible legacy yet.